MYOELECTRIC ACTIVITY OF THE CECUM AND PROXIMAL LOOP OF THE ASCENDING COLON IN COWS

Six Jersey cows were implanted with 8 pairs of bipolar electrodes: 1 i n the jejunum, 1 in the ileum, 3 in the cecum, and 3 in the proximal l oop of the ascending colon (PLAC). Myoelectric activity was recorded a t 2- to S-day intervals, 3 times for 8 hours or 4 times for 6 hours, u sing a computer-based oscillograph and data-acquisition program. Mean (+/- SD) duration of the migrating my oelectric complex (MMC) in the i leum was 84.52 +/- 4.87 minutes. Phases I and II of the MMC lasted sig nificantly (P < 0.05) longer than phase III, Two types (A and B) of c yclic activity were found in the cecum and PLAC. Cyclic activity type A was observed predominantly in the cecum, and type B was observed exc lusively in the PLAC. Phase III of the MMC in the ileum was accompanie d by hyperactivity type A at the level of the ileocecocolic junction i n 60.90 +/- 12.65% of the MMC. Twenty-seven types of orally and aboral ly propagated spike sequences, involving the cecum and PLAC, were foun d. They were most frequent when an MMC phase III was observed in the i leum, and least frequent when an MMC phase I was observed in the ileum (P < 0.05). All electrode sites of the cecum and PLAC served as pacem aker areas. Propagated and nonpropagated spikes were found at all elec trode sites df the cecum and PLAC. Although propagated spikes lasted s ignificantly (P < 0.05) longer than nonpropagated spikes, a clear dist inction on the basis of duration could not be defined between the 2 sp ike types because broad overlapping of duration existed. Duration of c ecocolic spiking activity per electrode (expressed as percentage of ti me) was significantly (P < 0.05) greater during MMC phase III in the i leum than during MMC phase I. It can be concluded that myoelectric act ivity of the cecum is well coordinated with the ileum and the PLAC. Ph ases of reduced and increased myoelectric activity in the cecum and PL AC are simultaneous with phases I and III of the MMC in the ileum.